3MAX
1/2 ton status
Does anyone have a diagram, or can at least walk me through how the compressor clutch should be wired up? I've searched here and other sites with no luck.
CK5
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AC wiring diagram for 1990 Blazer
- Thread starter 3MAX
- Start date
3MAX
1/2 ton status
I've continued to search for how just how the system should operate - High & low pressure switches, etc. This is one area I know little about. I believe I'm getting closer to the point of being able to trouble shoot my AC.
Can anyone confirm whether or not the ECU has any bearing on when the compressor clutch operates, or if it receives a signal from the clutch?
Can anyone confirm whether or not the ECU has any bearing on when the compressor clutch operates, or if it receives a signal from the clutch?
Can't confirm 100%, but I think the A/C components and operation didn't change from 85-91 in Blazers. There should be a plug with two wires that goes into the compressor, and a ground wire. there is a two-wire plug that goes into the pressure switch, which is located on the side of the accumulator. Basically, all that switch does is close the circuit if there is sufficient pressure in the system, and allow the clutch to engage.
If the ECU has any bearing on operation, I would think it would only be involved in idling up the engine when the A/C is turned on, which was accomplished by a solenoid prior to fuel injection.
These wiring diagrams may prove useful:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=11766.0
If the ECU has any bearing on operation, I would think it would only be involved in idling up the engine when the A/C is turned on, which was accomplished by a solenoid prior to fuel injection.
These wiring diagrams may prove useful:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=11766.0
I have the factory electrical manual, but no way to scan it...
3MAX
1/2 ton status
Thanks. The links don't show the AC system wiring.
My wiring was a mess when I got this Blazer. I've got everything straightened out except the AC.
The plug going to the compressor clutch has power to both wires - 12.6v with the AC selector turned off, and 13.4v with it turned on. Obviously the clutch is not engaging with power to both wires.
The compressor has a single-wire high pressure switch in the back of it, but it's not hooked up. From what I've read, I don't think the original compressor had a high pressure switch, so I assume this one was swapped in.
I'm just trying to figure out how everything should be wired up to get it going. Should power be routed through the low pressure switch and then to the clutch? I assume one wire going to the clutch is for ground? Does the high pressure switch connect to ground? I'd like to wire it in as well.
3MAX
1/2 ton status
Could you take a picture of the wiring diagram and post it?
3MAX
1/2 ton status
A
Alright - I believe I've got everything wired up correctly. The compressor is operating and the system is now blowing cold air, but only for a couple of minutes. The high pressure switch is kicking the compressor off after only a couple of minutes of running, then it will cycle about every 30 seconds or so (high pressure switch continuing to cycle).
I've read that R134a runs a higher pressure than R12 (the system was just charged with R134a). The high pressure switches appear to be color coded for various pressures, but I haven't found info to tell me which one I need. Can anyone confirm what color switch should be used with R134a?
Alright - I believe I've got everything wired up correctly. The compressor is operating and the system is now blowing cold air, but only for a couple of minutes. The high pressure switch is kicking the compressor off after only a couple of minutes of running, then it will cycle about every 30 seconds or so (high pressure switch continuing to cycle).
I've read that R134a runs a higher pressure than R12 (the system was just charged with R134a). The high pressure switches appear to be color coded for various pressures, but I haven't found info to tell me which one I need. Can anyone confirm what color switch should be used with R134a?
Not sure when they went to the computer control system for the AC, but the only thing I have that shows AC stuff is from 94, and its just a block diagram.
But it might help if your system is the newer type.
But it might help if your system is the newer type.
Have you hooked up a set of A/C pressure gauges? Frequent cycling of the clutch may indicate a low charge. Are you certain it's the high side switch cutting out the clutch, and not the low pressure switch?
As for the color code, I'm not sure what the difference is, although they do appear to make ones for OEM and for 134 retrofit...
http://www.autopartswarehouse.com/shop_parts/a-fs-c_switch/chevy.html
3MAX
1/2 ton status
The high pressure switch breaks the ground when it kicks out and the low pressure kills the +12v. I was checking it with a meter to see which side I lost at the clutch, so I'm sure it's the high pressure switch.
I have not checked the pressures with gauges - I don't have a set. Mechanic said he put a full charge it it, so I'm taking his word for it (which may be a mistake
)
yes sir, I'll work on it tomorrow...
BTW, the switch attached to your receiver/dryer should be adjustable...
Remove the plug, there should be a screw inside that "fine tunes" the pressure controlling the cycling points for the compressor.
I did mine 2 weeks ago.
FWIW, I have a '90 'burb & manual.
BTW, the switch attached to your receiver/dryer should be adjustable...
Remove the plug, there should be a screw inside that "fine tunes" the pressure controlling the cycling points for the compressor.
I did mine 2 weeks ago.
FWIW, I have a '90 'burb & manual.
3MAX
1/2 ton status
yes sir, I'll work on it tomorrow...
BTW, the switch attached to your receiver/dryer should be adjustable...
Remove the plug, there should be a screw inside that "fine tunes" the pressure controlling the cycling points for the compressor.
I did mine 2 weeks ago.
FWIW, I have a '90 'burb & manual.
No need to bother with it - I think I have the wiring straightened out. Now I just need to figure out for sure why it's cycling like it is. Gonna replace the high pressure switch with one for R134a and go from there.
